Problem: $ { \left[\begin{array}{rrr}{2} & {1} & {2} \\ {1} & {1} & {-1}\end{array}\right]+\left[\begin{array}{rrr}{0} & {1} & {0} \\ {-1} & {1} & {0}\end{array}\right] = {?} } $
Answer: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rrr}{2}+{0} & {1}+{1} & {2}+{0} \\ {1}+{-1} & {1}+{1} & {-1}+{0}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{2} & {2} & {2} \\ {0} & {2} & {-1}\end{array}\right]}$